The invention relates to aftertreatment systems for internal combustion engine exhaust, and more particularly to chemical species injection mixing.
To address engine emission concerns, new standards continue to be proposed for substantial reduction of various emissions, including NOx and particulate emissions. Increasingly stringent standards will require installation of aftertreatment devices in engine exhaust systems. Some of the aftertreatment technologies require certain chemical species to be injected into the exhaust system. For example, HC or fuel is injected in some active lean NOx systems for NOx reduction, or in active diesel particulate filters (DPF) for regeneration to take place (oxidizing the soot and cleaning the filter), and urea solution is injected in selective catalytic reduction (SCR) systems for NOx reduction. These injected chemical species need to be well mixed with exhaust gas before reaching catalysts or filters for the systems to perform properly.
The present invention arose during continuing development efforts directed toward the above exhaust aftertreatment systems. In one aspect, a compact mixer is provided. In a system with exhaust flow along an axial direction, a longer mixing distance/time is enabled without increasing axial length.